The Research Domain Criteria (RDoC) initiative: A brief look

Even for non-researchers, it is important to be informed about the various initiatives that change the way we do science and, ultimately, the way scientists choose to spend government dollars. In the wake of the 10-year anniversary of RDoC’s inception [1], I would like to unpack this commonly misunderstood acronym that is popping up in clinical science and provide some insight on how it can help researchers and the general public.

The Current Problem

As a psychologist in training, I believe the field’s ultimate goal is to develop an understanding of psychological processes for the purpose of alleviating the burden of mental illness and associated problems (i.e., decreased employment, socioeconomic status disparities, homelessness and incarceration, worsening of comorbid medical conditions, etc.). Psychologists have traditionally used a divide and conquer approach — everyone working on their favored topic (i.e., a particular disorder or process) and using their favored methods, while remaining isolated from other researchers within and outside of psychology. In clinical psychology, some key problems with this approach stunt progress:

Individuals with the same diagnosis may (and often do) have vastly different symptom profiles. This occurs for two reasons: First, symptoms are phenomenological, meaning they are based on readily observable symptoms (i.e., changes a clinician or someone can notice and report such as behavior, mood, speech, etc.). A rater’s subjective understanding of that symptom may not be consistent with another rater. Either way, you get the diagnosis or do not. Second, the presence of a diagnosis is determined by an arbitrary accumulation of these symptoms that a panel of experts decided constitutes a single diagnosis. For example, a diagnosis of depression requires at least 5 out of 9 symptoms, but which 5 (or more) will likely differ by patient.

Individuals with one diagnosis may (and often do) have other diagnoses — we call this comorbidity. For example, those with “depressive” disorders are very likely to also have “anxiety” and/or “substance use” disorders. We have two major problems: First, comorbidity raises the question if these disorders are truly separable categories. Second, when studies select participants with a single disorder, to reduce confounding variables of comorbidity, results are seldom translatable to the majority of sufferers. These issues bring us to problem 3.

These phenomena (or symptoms) were not derived from or selected based on neural or physiological changes. Understanding the underlying neuro-bio-chemical mechanisms of these phenomena is often the objective of research, especially when considering treatment or intervention strategies. But uncovering such connections with our current categorization system can be difficult. The variability in symptom profiles for a given diagnostic group may wash out any differences or effects, making it difficult to pinpoint specific mechanisms. Moreover, because the various symptoms we have clustered into a given diagnosis are not based on particular psychological processes, the symptoms may (1) represent many processes and (2) be missing features of a particular process. Accordingly, pinpointing a single mechanism or neural marker by comparing such diagnostic categories becomes difficult since we may be including superfluous information or missing key information.

RDoC Sushi. This figure presents the flaws of current approaches to neuroimaging research and the alternate approach taken by RDoC that addresses some of these concerns. Illustration by Nora Maria Raschle, credit: http://bornascientist.com

A Potential Solution

One way to address these problems and questions is with an initiative put forth by the National Institute of Mental Health (NIMH) [2]. RDoC stands for Research Domain Criteria and is a suggested process for scientific inquiry. Instead of studying disorders, RDoC suggests studying psychological constructs that exist on a spectrum from typical to atypical functioning. A psychological construct, as defined by NIMH, is “a concept summarizing data about a specified functional dimension of behavior” like reward learning or working memory, for example.

Image of the RDoC Framework from the National Institute of Mental Health

Let’s break this down with a medical example: the term “cold” is not all that informative and can differ for everyone. Typically, you can determine if you have a cold by various units of analysis (e.g., changes in behavior like sleepiness or fatigue, taking your temperature, evaluating mucus levels or color, etc.) and those measurements tell you something about the severity of each of your symptoms. Extensive research on these symptoms has helped us understand their underlying causes (e.g., a rise in temperature is due to the production of certain compounds by white blood-cells that then flow through the bloodstream to the hypothalamus, a brain region that regulates temperature). These mechanisms resulting in your symptoms are what the treatment targets. You/your doctor then use this information about your specific symptoms to select the proper treatment – do you select a decongestant, cough suppressant, pain reliever, or a combination? No matter your choice, medication will contain compounds that treat the individual symptoms across severity levels.

RDoC very much follows this model, suggesting that instead of studying an entire syndrome (i.e., a clinical disorder like “depression”) we study the various symptoms (i.e., psychological processes like memory, learning, reward processing, etc.) across units of analysis (i.e., behavioral tasks and observations, self-report, physiology, circuits, cells, genes, etc.) to understand how these processes function and may become disrupted.

RDoC may help advance psychological science, but this new way of thinking also has implications for the public. The ultimate goal of RDoC is to improve our understanding of psychological constructs to better the development of targeted treatments and precision medicine. Instead of trying to treat a host of phenomena with a single “cure,” we can focus on treating an underlying variation more specifically, providing a treatment that takes into account the individual differences of a patient. Moreover, studying these individual constructs or processes may help researchers connect the dots to their underlying mechanisms, which could greatly improve treatment and intervention strategies.

Understanding root psychological process deficits may also help the public better understand mental health concerns. Unclear, stigmatizing labels, such as “depression,” can be broken down into manageable and concrete symptoms, such as “abnormal sleep-wake cycle” or “decreased sensitivity to reward.” This may also help professionals distinguish clinically significant psychopathology from colloquial uses of diagnostic categories. The ability to talk about mental health problems in this way may increase effective communication between healthcare providers and patients and their families, and increase understanding from the community.

Helping people and society get healthier is a goal we can all embrace and if our current methods are not successful, it seems imperative that we seek new approaches. RDoC does not claim that its approach is the solution and in fact some problems with the initiative have been outlined [3,4] and other methods have been developed, but we should not run the risks of stagnation over the risks of novelty.

Acknowledgement: I would like to thank Dr. Bruce Cuthbert of the NIMH RDoC Unit for reading over an earlier draft of this post.